A unit fuel injector (30) has a boundary edge filter. A first endless annular internal space (100) is open to a holes (92) forming a fuel inlet port, a second endless annular internal space (102) that is spaced axially of the first endless annular internal space and through which fuel is supplied to an injection mechanism, and a series of circumferentially spaced apart, axially extending channels (104) through which fuel can pass from the first endless annular internal space to the second endless annular internal space.